In networked systems, the interconnect or the core switch fabric connecting the various system element, essentially attempts to connect N inputs to M outputs for the maximum number of possible routes. The “Non-Blocking” nature of the interconnection or the availability of “Clear Channels” enables the switch fabric to route or switch individual data packets.
In one interconnection architecture, the core switch fabric is based on time-domain multiple access (TDMA) to a common backplane or a shared bus. A controller, together with software, acts as the bus master and implements the routing kernel. The routing kernel is usually implemented in an algorithm such as a Hierarchical Weighted Fair Queuing algorithm.
Alternatively, the core switch fabric may be based on single or multiple crossbar integrated circuits. In this case, the controller asserts appropriate read and write commands to the crossbar and controls the exchange of data with a set of input and output buffers, typically constructed from common memory elements such as DRAM and SRAM. Switches are then built by using multiple cards which connect to the multiple input and output ports of the crossbar with a non-blocking switch fabric.
In any event, the devices interfacing with the switch fabric are reaching higher and higher speeds. This in turn requires higher throughput rate through the switch fabric itself. Existing systems calculate aggregate throughput, in bits per second, by taking the throughput in bits per second for one port of the switch fabric and multiplying it by the total number of input and output ports. This aggregate capacity can be increased by varying the number of input and output ports on the switch fabric, the speed of operation of the switch fabric and the efficiency of the network processor. Notwithstanding, device physics and the electrical characteristics of busses and interconnects are still significant limiting factors on throughput speed.
Consequently, a switch element is required, which taken individually or in conjunction with other elements of a similar type, enables the design and fabrication of high speed scalable switch fabrics.